Telechelic polymers, which are polymers that contain chemically reactive groups at both ends of the molecular chains, are used in large volumes in a number of industries. They find wide use as sealants, adhesives, propellant binders and materials of construction. However, these telechelic polymers are commercially available in a limited number of grades or characteristics and one frequently needs such polymers with properties different from those commercially available. For instance, in the propellant industry, carboxyl or hydroxyl terminated polybutadiene may be required with a particular reactive groups content and viscosity which cannot be matched with any prepolymer which he can purchase. To avoid the expense of synthesizing, from start, a polymer with the desired properties, it would be much more advantageous to modify the properties of a polymer which is already commercially available.